The present invention relates generally to the ability to provide a uniform application of polymeric diphenylmethane diisocyanate (pMDI) onto cellulose gypsum panels, boards and other surfaces, to create a substrate with increased strength and water resistance.
Exterior wall cladding is used as a barrier to keep exterior air and moisture out of the wall cavity. If water and moisture penetrate the wall cladding surface damage will result to the cladding board itself. Prior art exterior wall cladding was made out of gypsum sheathing or water-resistant gypsum board. It was found that the application of pMDI to a cellulose/gypsum based board greatly increased the board's strength and water resistance. The disclosed invention applies the pMDI to the cellulose/gypsum based board with an apparatus that provides a uniform coating across the board which results in increased water resistance and flexural strength.